The following picture shows a parental molecule of DNA The C

The following picture shows a parental molecule of DNA. The -CH_3 indicates the methyl groups associated with the DNA. Draw the two daughter DNA duplexes shortly after DNA replication and indicate which strand(s) is/are methylated. Draw the daughter DNA duplexes after several minutes have elapsed and indicate which strand(s) is/are methylated.

Solution

a) This concept is clearly to state how methylation happens after any DNA replication. Basically the parental starnd carries the methylation in the DNA strand and while replication happens there is a specific DNA methylase known as \"dam methylase\" which methylates the newly syanthesized DNA.

Now we will see what happens shortly after the DNA replication. Lets say the DNA has this code

G A(CH3) T C G A T C G A T C

C T A(CH3) G C T A G C T A G ------ This original parental strand would separate and form their respective daughter starnd keeping one of their parental strand with them,

Now look at one daughter starnd -

G A(CH3) T C G A T C G A T C

C T A G C T A G C T A G---------- New starnd immedietly will be non-methylated. This newly formed starnd is known as \"Hemi methylated DNA\", this is particularly because newly formed strand attached to the membrane and the inhibitor never helps the methylation to form instantly.

b) The previous explanation answers the second part, we can see as-

G A(CH3) T C G A T C G A T C

C T A(CH3) G C T A G C T A G---------(newly formed starnd I)

G A(CH3) T C G A T C G A T C

C T A(CH3) G C T A G C T A G---------(newly formed starnd II), all other starnds would be methylated as the cell has got enough time to open up the \"Hemi methylated Strands\" from the membrane inhibitors and then methylate them accordingly.